Low-color pvb sheet and a process for making same

ABSTRACT

The present invention is a low-color plasticized PVB sheet and a process for preparing the same. The sheet of the present invention yields a YID measurement of less than 12. A sheet of the present invention is useful for making glass laminates that are useful in cars, boats, trains, buildings, and display cases, for example.

This application claims the benefit of U.S. Provisional Application No.60/363,943, filed Mar. 12, 2002.

BACKGROUND OF THE INVENTION

Plasticized polyvinyl butyral (PVB) sheet is used in the manufacture oflaminate structures such as, for example: windshields for vehiclesincluding automobiles, motorcycles, boats and airplanes; homes andbuildings; shelving in cabinets and display cases; and other articleswhere structural strength is desirable in a glass sheet. In manyapplications, it is desirable that the laminate be transparent andcolorless, or at least have very low color. Undesired or unintendedcolor in a glass laminate can be a result of impurities from varioussources. In some cases, color can occur in the PVB interlayer. Color ina PVB sheet can result from several sources in the PVB resin, or fromthe manufacturing process. For example, color can result frominstability of the PVB resin, from impurities, or from other additivespresent in the PVB composition. Color in a PVB sheet can develop duringstorage of the PVB, or be caused by process conditions to which theresin is subjected.

Conventional PVB sheet typically includes a plasticizer in order toincrease the flexibility and processibility of the PVB sheet. Generally,the higher the concentration of plasticizer, the more flexible thesheet. Various plasticizers are conventional in the manufacture of PVB,and include such plasticizers as: diesters of polyethylene glycols suchas triethylene glycol di(2-ethylhexanoate) (3GO) and tetraethyleneglycol diheptanoate (4G7), for example. These examples are notall-inclusive of known plasticizers useful for preparing PVB sheeting.Typically, plasticizer is included in amounts of greater than 30 partsper hundred (pph), based on the total weight of the resin. Dependingupon the application, as well as other factors, highly plasticized PVBtypically can have as much as 60 pph of plasticizer.

In a conventional PVB sheet manufacturing process, additives aretypically included to protect PVB from developing color, to improve themanufacturing process, or to impart desirable properties orcharacteristics to the sheet. Examples of such additives are:antioxidants, such as octyl phenol for example; light stabilizers;surfactants; and adhesion control additives.

Manufacturers are continually looking for opportunities to improve theprocess or the properties of the product. For example, combinations oflight stabilizers can be required for optimum performance inconventional PVB compositions. Conventional PVB sheet compositions caninclude, for example, Tinuvin® P, Tinuvin® 123 in addition to Tinuvin®326 to obtain satisfactory light stability in the sheet. However, usingcombinations of light stabilizers can add additional expense andcomplexity to the manufacturing process, which is not desirable.

One other problem faced by PVB manufacturers is that changing onecomponent or additive in the polymer recipe can affect the performanceof other additives, or change the quality or performance of the finalsheet. There can be totally unexpected problems or benefits that resultfrom a change in the composition of a polymer recipe. For example,Applicants have discovered that the effectiveness of a particularantioxidant can be dependent upon the plasticizer used. For example, theApplicants surprisingly have found that antioxidants that are effectivein combination with 4G7 as plasticizer are not as effective when using3GO plasticizer.

It can be desirable to have a process for preparing a plasticized PVBsheet composition, whereby the color of the PVB sheet can be improvedwith the proper selection of additives. It is a further object of thepresent invention to have a process for manufacturing PVB that utilizesa plasticizer and a compatible antioxidant/additive package.

SUMMARY OF THE INVENTION

In one aspect, the present invention is a plasticized PVB sheetcomposition consisting essentially of: polyvinylbutyral having ahydroxyl (OH) number of from about 15 to about 20; a plasticizer orplasticizer mixture present in an amount of from about 30 parts perhundred (pph) to about 50 pph, based on the dry weight of the PVB resin;a surfactant; and optionally including either (i) a PVB bleachingcompound, or (ii) an antioxidant and an ultraviolet (UV) lightstabilizer, or (iii) both (i) and (ii), wherein the sheet has ayellowness index (YID) color of less than 12.

In another aspect the present invention is a process for preparing a lowcolor, PVB sheet comprising the steps: (I) admixing polyvinyl alcohol,butyraldehyde, an acid or mixture of acids, water, and a surfactant (II)stabilizing the mixture obtained in step (I) by (a) raising the pH ofthe mixture to at least pH 10 (b) isolating the resin by draining theliquid, (c) washing the resin with neutral pH water; (III) plasticizingthe PVB resin composition with from about 30 to about 50 pph ofplasticizer based on the dry weight of the PVB resin; (IV) optionallymixing (a) a PVB bleaching compound and/or (b) an antioxidant and a UVlight stabilizer with the PVB resin composition; and (V) extruding thePVB resin composition at a temperature of from about 175° C. to about225° C. to obtain a PVB sheet having a glass transition temperature(T_(g)) of greater than about 32° C. and a YID of less than about 12.

In still another aspect, the present invention is a laminate articlecomprising at least one layer of plasticized PVB sheet, wherein the PVBsheet consists essentially of: polyvinylbutyral having a hydroxyl (OH)number of from about 15 to about 20; a plasticizer or plasticizermixture present in an amount of from about 30 parts per hundred (pph) toabout 50 pph, based on the dry weight of the PVB resin; a surfactant;and optionally including either (i) a PVB bleaching compound, or (ii) anantioxidant and an ultraviolet (UV) light stabilizer, or (iii) both (i)and (ii), wherein the sheet has a yellowness index (YID) color of lessthan 12.

DETAILED DESCRIPTION

In one embodiment, the present invention is a plasticized PVB sheetcomposition comprising from about 30 to about 50 pph of a plasticizer.PVB can be manufactured according to known processes. For example, U.S.Pat. No. 3,153,009 describes a process for commercial manufacture ofPVB. U.S. Pat. No. 4,696,971 also describes a process for manufacturingPVB wherein sodium dioctyllsulfosuccinate (DOSS) is used as asurfactant.

The term flake, as used in the present invention, describes a particularphysical form of PVB resin material, that is, granular or particulateversus a film or a sheet. The physical form of the resin does notnecessarily indicate a different PVB composition within the presentapplication, even though sheets and/or films may include additives notfound in the resin flake.

A PVB of the present invention includes a plasticizer. Plasticizers ofthe present invention can chosen from any that are known or usedconventionally in the manufacture of plasticized PVB sheetingcompositions. For example, a plasticizer suitable for use herein can bea plasticizer or a mixture of plasticizers selected from the groupconsisting of: diesters obtained from the chemical reaction of aliphaticdiols with carboxylic acids, including diesters of polyether diols orpolyether polyols; and, esters obtained from polyvalent carboxylic acidsand aliphatic alcohols. For convenience, when describing the sheetcompositions of the present invention, a mixture of plasticizers can bereferred to herein as “plasticizer”. That is, the singular form of theword “plasticizer” as used herein can represent the use of either oneplasticizer or the use of a mixture of two or more plasticizers in agiven sheet composition. The intended use will be apparent to a readerskilled in the art. Preferred plasticizers for use herein are diestersobtained by the reaction of triethylene glycol or tetraethylene glycolwith aliphatic carboxylic acids having from 6 to 10 carbon atoms; anddiesters obtained from the reaction of sebacic acid with aliphaticalcohols having from 1 to 18 carbon atoms. More preferably theplasticizer is either 4G7, 3GO or dibutyl sebacate (DBS). Mostpreferably the plasticizer is 3GO.

The composition of the present invention optionally includes at leastone PVB bleaching compound. A PVB bleaching compound (bleachingcompound) of the present invention is any compound that can reduce oreliminate color from a PVB sheet relative to the color of an otherwiseidentical composition, treated using an identical or similar process,with the exception that a bleaching compound is not present. The mode ofthe bleaching action demonstrated by the bleaching compound is notcritical to the present invention. For example, a bleaching compounduseful in the practice of the present invention can be a compound thatreacts directly with color-forming compounds (color bodies) present in aPVB sheet composition, or a compound that is capable of yielding acompound that reacts directly with color-bodies. A bleaching compoundcan be a compound that can decompose in situ to yield decompositionproducts capable of reacting with color bodies present in a PVB sheetcomposition. A bleaching compound in the practice of the presentinvention can be a compound that inhibits the formation of color bodies.Bleaching compounds of the present invention include, for example,inorganic bisulfites such as sodium or potassium bisulfite; organicbisulfites such as tetramethylammonium bisulfite; and compounds similarin structure or function. Bleaching compounds also includesulfosuccinates such as dialkyl sulfosuccinates. For example, thepresent invention can include DOSS as a bleaching compound.

A bleaching compound of the present invention can be included in anyeffective finite amount. An effective amount for the purposes of thepresent invention is any amount that reduces the color of a PVB sheetrelative to the color of an identical or substantially similar PVB sheetcomposition without the bleaching compound. Color measurement can bedone according to any conventional standard practice. Alternatively, inthe absence of comparative data, an effective amount is any amount thatreduces the color of a PVB sheet to a yellowness index (YID) of lessthan about 12 YID. Preferably the YID is less than about 10, morepreferably less than about 8, and most preferably less than about 6.

A bleaching compound can be included in an amount of from about 0.01 toabout 0.85 pph, based on the weight of polyvinyl alcohol (PVA) used inthe preparation of PVB. Preferably, the bleaching compound is present inan amount of from about 0.05 to about 0.80 pph, more preferably in anamount of from about 0.10 to about 0.75 pph, and most preferably in anamount of from about 0.15 to about 0.70 pph. While color reduction in aPVB sheet is an important consideration, the amount of bleachingcompound included will also be a function of the cost of production andthe other properties that may be affected by including the additive.

The present invention includes a surfactant. A surfactant suitable foruse herein can be any that is known to be useful in the art ofpolyvinylbutyral manufacture. For example, surfactants suitable for useherein include: sodium lauryl sulfate; ammonium lauryl sulfate; sodiumdioctyl sulfosuccinate; ammonium perfluorocarboxylates having from 6 to12 carbon atoms; sodium aryl sulfonates, adducts of chlorinatedcyclopentadiene and maleic anhydride; partially neutralizedpolymethacrylic acid; alkylaryl sulfonates; sodium N-oleyl-N-methyltaurate; sodium alkylaryl polyether sulfonates; triethanolamine laurylsulfate; diethyl dicyclohexyl ammonium lauryl sulfate; sodiumsecondary-alkyl sulfates; sulfated fatty acid esters; sulfated arylalcohols; and the like. Preferable surfactants include sodium laurylsulfate, sodium dioctyl sulfosuccinate, sodium cocomethyl tauride, anddecyl(sulfophenoxy)benzenesulfonic acid disodium salt.

The surfactant can be included in any effective amount for theparticular set of process conditions practiced. The surfactant can beincluded in an amount of from about 0.01 to about 0.85 pph by weight,based on the weight of PVA used to prepare PVB. Preferably thesurfactant is included in an amount of from about 0.10 to about 0.80pph. More preferably, the surfactant is included in an amount of fromabout 0.15 to about 0.75 pph. Most preferably, the surfactant isincluded in an amount of from about 0.15 to about 0.70 pph.

The surfactant and the bleaching compound can be the same compound, orcan perform both functions. The bleaching compound is optional only inthe event that the surfactant can also perform the function of ableaching compound. Otherwise the bleaching compound is considered to beessential in the practice of the present invention. For example, DOSScan be used in the practice of the present invention as a surfactant.DOSS can also be a bleaching compound in the practice of the presentinvention. In one particularly preferred embodiment, DOSS can beincluded as both a surfactant and as a bleaching compound. In thisembodiment, the use of a bleaching compound other than DOSS is optional.

Antioxidants can be optionally included in a PVB resin composition ofthe present invention during sheet preparation to inhibit the oxidationof the PVB resin and/or components. Preferred antioxidants are knownconventionally and available commercially. Most preferred arebis-phenolic antioxidants, which are surprisingly more suitable forpreparing low color PVB sheeting, particularly when 3GO is used asplasticizer. Bis-phenolic antioxidants are available and can be obtainedcommercially. Suitable bis-phenolic antioxidants include2,2′-ethylidenebis(4,6-di-t-butylphenol);4,4′-butylidenebis(2-t-butyl-5-methylphenol);2,2′-isobutylidenebis(4,6-dimethylphenol); and2,2′-methylenebis(6-t-butyl-4-methylphenol), for example. Bis-phenolicanti-oxidants are commercially available under the tradename of ANOX™29, LOWINOX® 22M46, LOWINOX® 44B25, and LOWINOX® 22IB46, for example.

An antioxidant can be included in any effective finite amount.Preferably, the antioxidant is included in an amount of from about 0.01to about 0.6%, based on the total weight of the sheet. More preferably,the antioxidant is present in amount of from about 0.03 to about 0.3%,most preferably in an amount of from about 0.05 to about 0.25%.

Other additives are known conventionally to be useful, and can beincluded in a resin composition of the present invention. Such additivesinclude: light stabilizers, particularly UV light stabilizers, such asTinuvin® P; Tinuvin® 326, and Tinuvin® 123. UV light stabilizers canstabilize the PVB composition by absorbing ultraviolet light andpreventing unwanted effects by the UV light on the PVB. Adhesion controlagents such as alkali and alkaline earth metal salts of carboxylicacids, alkaline earth metal salts of inorganic acids, or a combinationof such salts can be added. Surface tension controlling agents such asTrans® 290 or Trans® 296 available from Trans-Chemco; or Q2-3183A®available from Dow Chemical can be used in the practice of the presentinvention. The use of Trans® 290 or Trans® 296 is preferred.

A PVB resin of the present invention can be obtained by processes knownin the art of PVB manufacture. PVB resins used in the practice of thepresent invention can be prepared by mixing PVA with butyraldehyde in anaqueous medium in the presence of an acid or mixture of acids, at atemperature of from 5° C. to 100° C.

Typically, the ratio of PVA to butyraldehyde can be chosen such that thePVB has residual hydroxyl functionality, conventionally reported as OHnumber. Residual hydroxyl functionality can vary according to whatproperties are desirable in the PVB. The relative amounts ofbutyraldehyde and PVA required to obtain the desired OH number in thePVB resin will be readily apparent to those skilled in the art of PVBmanufacture. In the practice of the present invention residual hydroxylcan be in the range of from about 14 to about 30. Preferably, the OHnumber is from about 15 to about 25. More preferably, the OH number isfrom about 15 to about 20, and most preferred in the practice of thepresent invention is PVB resin having an OH number in the range of fromabout 17 to about 19. The OH number can be determined according tostandard methods such as ASTM D1396-92.

In a preferred embodiment, a low color PVB resin of the presentinvention can be obtained by a process comprising the steps: (I)admixing polyvinyl alcohol, butyraldehyde, an acid or mixture of acids,water, and a surfactant (II) stabilizing the mixture obtained in step(I) by (a) raising the pH of the mixture to at least pH 10 (b) isolatingthe resin by draining the liquid, (c) washing the resin with neutral pHwater; (III) plasticizing the PVB resin composition with from about 30to about 50 pph of plasticizer based on the dry weight of the PVB resin;(IV) optionally mixing (a) a PVB bleaching compound and/or (b) anantioxidant and a UV light stabilizer with the PVB resin composition;and (V) extruding the PVB resin composition at a temperature of fromabout 175° C. to about 225° C. to obtain a PVB sheet having a T_(g) ofgreater than about 32° C. and a YID of less than about 12.

The steps of the process described herein can be carried out in variedorder. For example, while it can be necessary to carry out step (I)before step (II) it is not essential, for the purpose of obtaining a lowcolor sheet of the present invention, that steps (III) or (IV) becarried out in any particular order. Although it may be preferable toimplement these steps just prior to, or simultaneous with, step (V).Also, the order of addition of components is not critical in thepractice of the present invention, although a skilled artisan willrecognize that there may be other benefits of carrying out the processin a consistent and ordered manner. For example, plasticizer can bemixed with the PVB either before or during the extrusion of the PVBcomposition, as described in U.S. Pat. No. 5,886,075.

Plasticizer can be added in any amount desirable to obtain a plasticizedPVB sheet. Plasticizer can be added in an amount of from about 30 toabout 50 pph, based upon the total dry weight of the resin. The “dryweight” as used herein refers to the weight of the dry resin, that is,after water has been removed from the resin. Preferably the plasticizeris present in an amount of from about 30 to about 45 pph, and mostpreferably in an amount of from about 32 to about 45 pph.

Plasticization can be carried out using either a “wet” process or a“dry” process. The wet process, as the term is used herein, is a processwhereby the plasticizer is mixed with a PVB resin aqueous slurry,together with other additives, prior to, or as, the mixture is fed intoan extruder. A residence time of from 2 to 24 hours for theplasticizer/PVB mixture can be preferred prior to sending the mixture toan extruder. A wet process suitable for use herein is described in U.S.Pat. No. 3,153,009, for example. A dry process, as the term is usedherein, is a process whereby the plasticizer is mixed with the dry PVBresin flake prior to, or as, the mixture is fed into an extruder. A dryprocess suitable for use herein is described in U.S. Pat. No. 5,886,075, for example.

The T_(g) of a PVB sheet of the present invention, as measured byDynamic Mechanical Analysis (DMA) is dependent upon the concentration ofplasticizer included in the composition. In the practice of the presentinvention, a sheet has a T_(g) of from about 32° C. to about 50° C.Preferably, the T_(g) is from about 33° C. to about 47° C., and morepreferably from about 35° C. to about 45° C.

A low color PVB resin sheet suitable for the purposes herein can beobtained by a process that comprises the steps of: (1) isolating PVBflake from a PVA/butyraldehyde reaction mixture previously describedherein; (2) optionally admixing an antioxidant and a UV light stabilizerwith the plasticizer to obtain a plasticizer/additive mixture(plasticizer mixture); and (3) co-extruding the flake, plasticizer,antioxidant, and UV light stabilizer, or alternatively co-extruding theflake and the plasticizer mixture at a feed ratio of plasticizer mixtureto dry of flake from about 30:100 (wt:wt) to about 50:100 (wt:wt) at atemperature of from about 175° C. to about 225° C. to obtain a low-colorPVB resin having a YID of less than about 12. It is preferable to admixthe antioxidant/UV light stabilizer with the plasticizer prior toextrusion of the resin.

EXAMPLES

The following Examples and comparative examples are presented to furtherillustrate the present invention. The Examples are not intended to limitthe scope of the invention in any manner, nor should they be used todefine the claims or specification in any manner that is inconsistentwith the invention as claimed and/or as described herein.

The following tests were used in the examples and comparative examplesbelow.

Hydroxyl number: ASTM D 1396-92.

Sheet yellowness index (YID): A chip is made with 21.0 grams of sheet,and heat pressed into a 10.0 mm thick disk of 50.8 mm diameter. Chippreparation involves preheating a stack of 50.8 mm disks cut from thesheet in a mold for one minute at 2200 N force and 185° C., thenincreasing the pressing force to 32,000 N at 185° C. for two minutes,and cooling under the same force for 7.5 minutes. No residual surfacepattern that was on the extruded sheet is visible in the chip.Yellowness index was determined per ASTM D1925-70 on the 10.0 mm thickchip.

Flake Yellowness Index (YID)

A “chip” specimen is made from 21.0 grams of dried PVB resin (akaflake). Flake moisture should be less than 0.2% prior to chippreparation. The dried flake is heat pressed into a 1-cm thick, 5.08-cmdiameter circular chip. Chip preparation involves hot pressing a the21.0 grams of dried PVB resin as follows: Press Cycle Time (min) Temp. °C. Force (N) a. Pre-heat 1.5 180 2220 b. Cure 2. 180 86700 c. Cool 8.086700The thickness of the chip is measured and recorded and the yellownessindex (YID) is then determined per ASTM D1925.Glass Transition Temperature—T_(g) is determined by DMA using theprocedure of ASTM D4065, using the tangent delta at 1 Hz.

Example 1

Poly(vinyl butyral) sheet was prepared as follows: at 90° C., a mixturecomprising 32 parts by weight of poly(vinyl alcohol) of average degreeof polymerization 618 and 99.5% hydrolyzed and 68 parts by weight of PVAof average degree of polymerization 1005 and 99.5% hydrolyzed wasdissolved in 615 parts by weight of demineralized water. To thissolution was added 1 part by weight of 88% para-toluene sulfonic acidand enough sulfuric acid to bring the dissolved PVA solution to a pH of2. Using the procedure described in U.S. Pat. No. 3,153,009, 62 parts byweight of n-butyraldehyde and 0.47 parts by weight of 70% DOSS and thePVA solution were charged into a vessel maintained at 90° C. After a onehour hold time, a Blurry was obtained and the slurry was stabilized witha sodium hydroxide solution to raise the pH to 11. Concurrent with thestabilization, 0.07 parts by weight Trans® 290 surface tensionstabilizing agent was added. The slurry was then washed and cooled withdemineralized water. A granular, white PVB resin with residual hydroxylnumber of 18.6 and flake YID of 8.8 was obtained. The flake was mixedwith 3GO plasticizer containing 4 grams per liter of Tinuvin® P and 8grams per liter of Lowinox® 44B25 antioxidant and was extruded so thatthe residence time in the extrusion system was about 15 to 25 minutes.The feed rate ratio of plasticizer to dry flake was 35:100 (wt:wt).Potassium formate solution was injected so as to deliver a potassiumconcentration of 10 parts per million (ppm) in the sheet. Melttemperature measured at the slot die was between 210 and 215° C. SheetYID was 5.85.

Comparative Example C1

PVB flake was prepared as in Example 1 except that 0.4 parts by weightof sodium lauryl sulfate was used in the place of DOSS as thesurfactant, and no other surface tension modifiers were added. Agranular, white PVB resin with residual hydroxyl number of 18.6 wasobtained. Using the flake made with sodium lauryl sulfate as describedhere, sheet was prepared as in Example 1. Melt temperature measured atthe slot die was between 210 and 213° C. Sheet yellowness was 25.05.

Comparative Example C2

Flake and sheet were made as in Example C1, except that 4 grams perliter of octylphenol was used in the place of Lowinox® 44 B25 asantioxidant in the plasticizer, and the potassium level was 300 partsper million (ppm). Sheet yellowness index was 13.57.

1. A process for preparing a low color, PVB sheet comprising the steps:(I) admixing polyvinyl alcohol, butyraldehyde, an acid or mixture ofacids, water, and a surfactant (II) stabilizing the mixture obtained instep (I) by (a) raising the pH of the mixture to at least pH 10 (b)isolating the resin by draining the liquid, (c) washing the resin withneutral pH water; (III) plasticizing the PVB resin composition with fromabout 30 to about 50 pph of plasticizer based on the dry weight of thePVB resin; (IV) optionally mixing (a) a PVB bleaching compound and/or(b) an antioxidant and a UV light stabilizer with the PVB resincomposition; and (V) extruding the PVB resin composition at atemperature of from about 175° C. to about 225° C. to obtain a PVB sheethaving a glass transition temperature (T_(g)) of greater than about 32°C. and a YID of less than about
 12. 2. The process of claim 1 wherein:(a) the resin composition is plasticized with from about 30 to about 50pph plasticizer; (b) the resin composition includes an antioxidant and aUV light stabilizer.
 3. The process of claim 2 wherein the antioxidantis a diphenolic compound.
 4. The process of claim 3 wherein the resincomposition is extruded at a temperature of from about 205° C. to about220° C.
 5. The process of claim 4 wherein the resin composition isextruded at a temperature of from about 210° C. to about 215° C.
 6. Theprocess of claim 2 wherein the surfactant is a dialkysulfosuccinate. 7.The process of claim 6 wherein the surfactant is DOSS.
 8. The process ofclaim 2 wherein the resin composition includes a PVB bleaching compound.9. The process of claim 8 wherein the bleaching compound is an organicbisulfite, an inorganic bisulfite, or a dialkylsulfosuccinate.
 10. Theprocess of claim 9 wherein the bleaching compound is DOSS.
 11. Theprocess of claim 10 wherein the PVB is plasticized using a wet process.12. The process of claim 10 wherein the PVB is plasticized using a dryprocess.
 13. An PVB sheet obtained by the process of any of claims 1-12.14. A plasticized PVB sheet composition consisting essentially of:polyvinylbutyral having a hydroxyl (OH) number of from about 15 to about25; a plasticizer or plasticizer mixture present in an amount of fromabout 30 pph to about 50 pph, based on the dry weight of the PVB resin;a surfactant; and optionally including either (i) a PVB bleachingcompound, or (ii) an antioxidant and an ultraviolet (UV) lightstabilizer, or (iii) both (i) and (ii), wherein the sheet has ayellowness index (YID) color of less than
 12. 15. The composition ofclaim 14 wherein the plasticizer is 3GO.
 16. The composition of claim 15wherein the plasticizer is present in an amount of from about 30 toabout 45 pph, by weight, based on the dry weight of the PVB resin. 17.The composition of claim 16 wherein the plasticizer is present in anamount of from about 35 to about 45 pph.
 18. The composition of claim 17wherein the PVB includes a surfactant, a bleaching compound, anantioxidant, and a UV light stabilizer.
 19. The composition of claim 18wherein the surfactant and the bleaching compound are the same compound.20. The composition of claim 19 wherein the surfactant is DOSS.
 21. Thecomposition of claim 20 wherein the antioxidant is a bis-phenoliccompound.
 22. The composition of claim 21 wherein the antioxidant is2,2′-methylenebis(6-t-butyl-4-methylphenol).
 23. A laminate articlecomprising at least one layer of the PVB composition of claim 14.